Nitrogen-vacancy (NV) color centers in diamond nanocrystals are a new class of external tags that have exceptionally high output, due to the absence of bleaching or blinking even after months of continuous excitation, yet with an instantaneous brightness comparable to fluorescent proteins. The diamond host material is also unsurpassed for chemical and biological inertness. These properties of NV nano-diamonds alone would open new frontiers for single-molecule tracking in cells. However NV nano-diamonds currently have three main weaknesses: 1) low spectral specificity, 2) large particle size, and 3) low specificity of surface functionalization. To improve the spectral specificity, the spin degree of freedom will be used. Specifically, two NV centers with sub-nanometer separation will be resolved using magnetic resonance imaging concepts. To reduce particle size while still maintaining the key properties of the NV center, ultra-pure diamond nanoparticles will be implanted with nitrogen. This will give a high enough concentration of NVs to ensure at least one per few nanometer sized nano-diamonds. To achieve highly specific functionalization, the surface of NV containing diamond nano-crystals will be modified to look like that of encapsulated quantum dots, so that most of the sophisticated functionalization techniques currently used for Q-dots will immediately become applicable. To accomplish this, we will first concentrate on the amino-silanization of oxygen terminated nano-diamond surfaces. Successful completion of this research will provide revolutionary new capabilities for the imaging and tracking of single molecules in cells that will ultimately lead to much better understanding of metabolic processes in living cells on the molecular scale, and lead to the better diagnosis and treatment of numerous diseases. This research will provide an unprecedented capability for the study of metabolic processes in living cells on the molecular scale. Such molecular-scale knowledge of cellular processes is critical for the advanced diagnosis and effective treatment of difficult diseases such as cancer and highly infectious diseases, including those anticipated in bio-terrorism.